Light-emitting device
A light-emitting device includes: a light-emitting stack including a first surface and a second surface opposite to the first surface, wherein the light-emitting stack emits a light having a wavelength between 365 nm and 550 nm; and a first electrode formed on the first surface and comprising a first metal layer and a second metal layer alternating with the first metal layer, wherein the first electrode has a reflectivity larger than 95% for reflecting the light, and the second metal layer has a higher reflectivity index relative to the light than that of the first metal layer.
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The application relates to a light-emitting device, and more particularly, to a light-emitting device comprising a reflective layer.
REFERENCE TO RELATED APPLICATIONThis application claims the right of priority based on TW application Serial No. 103112952, filed on Apr. 8, 2014, and the content of which is hereby incorporated by reference in its entirety.
DESCRIPTION OF BACKGROUND ARTThe lighting theory of light-emitting diodes (LEDs) is that electrons and holes between an n-type semiconductor and a p-type semiconductor are combined in the active layer to release light. Due to the difference of lighting theories between LEDs and incandescent lamps, the LED is called “cold light source”. An LED has the advantages of good environment tolerance, a long service life, portability, and low power consumption so it is regarded as another option for the lighting application. LEDs are widely adopted in different fields, for example, traffic lights, backlight modules, street lights, and medical devices and replace conventional light sources gradually.
An LED has a light-emitting stack which is epitaxially grown on a conductive substrate or an insulative substrate. The so-called “vertical LED” has a conductive substrate and includes an electrode formed on the top of a light emitting layer; the so-called “lateral LED” has an insulative substrate and includes electrodes formed on two semiconductor layers which have different polarities and exposed by an etching process. The vertical LED has the advantages of small light-shading area for electrodes, good heat dissipating efficiency, and no additional etching epitaxial process, but has a problem that the conductive substrate served as an epitaxial substrate absorbs light easily and is adverse to the light efficiency of the LED. The lateral LED has the advantage of radiating light in all directions due to a transparent substrate used as the insulative substrate, but has disadvantages of poor heat dissipation, larger light-shading area for electrodes, and smaller light-emitting area caused because of the epitaxial etching process.
The abovementioned LED can further connect to/with other components for forming a light-emitting device. For a light-emitting device, the LED can connect to a sub-carrier by the substrate side or by soldering material/adhesive material between the sub-carrier and the LED. Besides, the sub-carrier can further comprise a circuit electrically connected to electrodes of the LED via a conductive structure, for example, a metal wire.
SUMMARY OF THE APPLICATIONA light-emitting device comprises: a light-emitting stack including a first surface and a second surface opposite to the first surface, wherein the light-emitting stack emits a light having a wavelength between 365 nm and 550 nm; and a first electrode formed on the first surface and including a first metal layer and a second metal layer alternating with the first metal layer, wherein the first electrode has a reflectivity larger than 95% for reflecting the light, and the second metal layer has a higher reflectivity relative to the light than that of the first metal layer.
A light-emitting device comprises: a light-emitting stack comprising a first surface and a second surface opposite to the first surface, wherein the light-emitting stack emits a light having a wavelength between 365 nm and 550 nm, and the first surface comprises a first portion having a first conductivity and a second portion having a second conductivity; a first electrode, comprising a first electrode pad and a reflective stack comprising a first metal layer and a second metal layer alternating with the first metal layer, wherein the reflective stack is electrically connect to the first portion of the first surface and has a reflectivity larger than 95% for reflecting the light, and the second metal layer has a higher reflectivity relative to the light than that of the first metal layer; a second electrode, comprising a second electrode pad and an ohmic contact layer formed on the second portion of the first surface; and a carrier comprising a first contact pad electrically connected to the first electrode pad and a second contact pad electrically connected to the second electrode pad.
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Although the present application has been explained above, it is not the limitation of the range, the sequence in practice, the material in practice, or the method in practice. Any modification or decoration for present application is not detached from the spirit and the range of such.
Claims
1. A light-emitting device, comprising:
- a light-emitting stack, comprising a first surface and a second surface opposite to the first surface, wherein the light-emitting stack emits a light having a wavelength between 365 nm and 550 nm; and
- a first electrode formed on the first surface and comprising a first metal layer and a second metal layer alternating with the first metal layer, wherein the first electrode has a reflectivity larger than 95% for reflecting the light, and the second metal layer has a higher reflectivity index relative to the light than that of the first metal layer.
2. The light-emitting device of claim 1, wherein the second metal layer alternates with the first metal layer for 2 to 12 times.
3. The light-emitting device of claim 1, wherein the first metal layer comprises Al and the second metal layer comprises Ag.
4. The light-emitting device of claim 1, wherein the first metal layer comprises an alloy or stack comprising Al, Ti, W, Pt, and Ni.
5. The light-emitting device of claim 1, wherein the thickness of the first metal layer is between 1 Å and 10 Å, and the thickness of the second metal layer comprises is between 100 Å and 700 Å.
6. The light-emitting device of claim 5, wherein the thickness of the first metal layer is approximately 3 Å, and the first metal layer is discontinuous.
7. The light-emitting device of claim 1, wherein the first metal layer directly contacts the first surface.
8. The light-emitting device of claim 1, wherein the light-emitting stack comprises a first semiconductor layer comprising the second surface, a second semiconductor layer comprising the first surface and an active layer between the first semiconductor layer and the second semiconductor layer, and the first electrode is formed on a part of the first surface, and the light is emitted out the light-emitting stack from the second surface.
9. The light-emitting device of claim 8, further comprising a barrier layer formed on the first surface and covering the first electrode; a conductive substrate; and a conductive bonding layer formed between the conductive substrate and the barrier layer.
10. The light-emitting device of claim 8, further comprising a second electrode having a pattern formed on the second surface, and a current blocking layer formed on the first surface and corresponding to the location of the second electrode.
11. The light-emitting device of claim 10, wherein the current blocking layer is covered by the first electrode.
12. The light-emitting device of claim 1, wherein the first electrode has a reflectivity between 98% and 100% relative to the light.
13. A light-emitting device, comprising:
- a light-emitting stack comprising a first surface and a second surface opposite to the first surface, wherein the light-emitting stack emits a light having a wavelength between 365 nm and 550 nm, and the first surface comprises a first portion having a first conductivity and a second portion having a second conductivity;
- a first electrode, comprising a first electrode pad and a reflective stack comprising a first metal layer and a second metal layer alternating with the first metal layer, wherein the reflective stack is electrically connect to the first portion of the first surface and has a reflectivity larger than 95% for reflecting the light, and the second metal layer has a higher reflectivity relative to the light than that of the first metal layer;
- a second electrode, comprising a second electrode pad and an ohmic contact layer formed on the second portion of the first surface; and
- a carrier comprising a first contact pad electrically connected to the first electrode pad and a second contact pad electrically connected to the second electrode pad.
14. The light-emitting device of claim 13, wherein the second metal layer alternates with the first metal layer for 2 to 12 times.
15. The light-emitting device of claim 13, wherein the first metal layer comprises Al and the second metal layer comprises Ag.
16. The light-emitting device of claim 13, wherein the thickness of the first metal is between 1 Å and 10 Å, and the thickness of the second metal layer is between 100 Å and 700 Å.
17. The light-emitting device of claim 14, wherein the light-emitting stack comprises a first semiconductor layer comprising the second portion of the first surface and the second surface, a second semiconductor layer comprising the first portion of the first surface and the second surface, and an active layer between the first semiconductor layer and the second semiconductor layer, and the light is emitted out the light-emitting stack from the second surface.
18. The light-emitting device of claim 17, further comprising an insulating layer covering the first surface, and the first electrode pad and the second electrode pad are formed between a surface of the insulating layer and the carrier.
19. The light-emitting device of claim 18, wherein the first electrode further comprises a barrier layer covering between the first portion of the first surface and the insulating layer; and a first conductive channel penetrating through the insulating layer to connect to the first electrode pad and the barrier layer, and the second electrode pad further comprises a second conductive channel penetrating through the insulating layer to connect to the second electrode pad and the ohmic contact layer.
20. The light-emitting device of claim 13, wherein the first electrode has a reflectivity from 98% to 100% relative to the light.
7436066 | October 14, 2008 | Sonobe et al. |
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8482021 | July 9, 2013 | Kim et al. |
8492785 | July 23, 2013 | Hodota |
20120286309 | November 15, 2012 | Chae et al. |
Type: Grant
Filed: Apr 8, 2015
Date of Patent: Feb 16, 2016
Patent Publication Number: 20150287886
Assignee: EPISTAR CORPORATION (Hsinchu)
Inventors: Chi Hao Huang (Hsinchu), Siou Huang Liou (Hsinchu), Tz Chiang Yu (Hsinchu), Jennhua Fu (Hsinchu)
Primary Examiner: Cuong Q Nguyen
Application Number: 14/681,291
International Classification: H01L 33/00 (20100101); H01L 33/46 (20100101); H01L 33/40 (20100101); H01L 33/62 (20100101); H01L 33/14 (20100101);